This invention relates to a hydraulically operated loading apparatus, and, more particularly, to a control apparatus for operating the hydraulic functions of a hydraulically operated loading apparatus.
U.S. Pat. No. 4,012,069 describes a hydraulically operated loading apparatus for loading trash which is mounted on a vehicle and which loads trash into a container which is carried by the vehicle. The loading apparatus includes a main boom which is mounted on a rotating head, allowing vertical rotation. The rotating head, allowing horizontal rotation, is supported by a structural pedestal supported by the vehicle. The tip boom, mounted to the outer end of the main boom and allowing vertical rotation, also includes a telescoping tip extension for extending the length of the tip boom. A grapple or clamshell-type bucket is mounted on the end of the telescoping extension of the tip boom with a rotary swivel allowing continuous grapple.
The apparatus of the type which is described in U.S. Pat. No. 4,012,069 typically includes six hydraulic actuators. One of the actuators slews or rotates the main boom relative to the base. Other actuators raise and lower the main boom and the tip boom. Another actuator extends and retracts the tip boom extension. An actuator rotates the grapple, and a final actuator opens and closes the grapple. Each actuator is a double acting actuator which is controlled by a hydraulic valve which supplies pressurized hydraulic fluid to the actuator.
Each valve can be operated by a separate controller, e.g., a lever or handle for opening and closing the valve. Six valves require six separate controllers, which are difficult to operate by one person.
FIG. 1 illustrates one type of prior art control mechanism for operating hydraulic actuators. A rotating head 10 is mounted on a pedestal 11. An upper set of seven rods 12 and a lower set of four rods 13 are rotatably mounted in vertically extending plates 14 which are attached to the pedestal. Each of the upper rods 12 includes a horizontal center portion 12a and a pair of upwardly extending handle portions 12b. Each of the lower rods 13 includes a horizontal center portion 13a and a pair of rearwardly extending handle portions 13b. 
A valve bank 15 is mounted on the pedestal and includes a plurality of valve spool assemblies 16 for operating the hydraulic actuators of the device. A crank arm 17 is attached to each of the horizontal portions 12a and 13a so that movement of one of the handle portions 12b and 13b operates one of the valve spools. The two sets of handle portions permit the hydraulic actuators to be operated from either side of the pedestal.
FIGS. 2-4 illustrate another prior art control mechanism for operating hydraulic actuators. FIG. 2 illustrates a seat 20 in a rear facing load cab. Right and left three-function joysticks 21 and 22 are mounted on the right and left sides of the seat.
The joystick 22 on the left side of the seat controls three hydraulic valve spools 23-25 (FIG. 3). The three spool hydraulic control valve is mounted beneath the floor of the control cab (indicated in phantom outline in FIG. 3) for reduction in noise and heat. In each case, moving the joystick causes one of three reach rods 26, 27, and 28 extending through the floor to move a hydraulic valve spool that then directs pressurized hydraulic fluid to actuate a hydraulic motor or hydraulic cylinder. Moving the joystick to the left actuates the valve spool that causes the loader to slew to the left; just as moving the joystick to the right causes the loader to slew to the right. Moving the joystick back extends the lift cylinder and raises the main boom. Conversely, moving the joystick forward lowers the main boom. Rotating the joystick counterclockwise to the left extends the tip extension boom. Rotating the joystick to clockwise to the right retracts the tip extension boom.
The joystick 21 on the right side of the seat controls three each hydraulic valve spools of another valve mounted under the floor of the control cab. Moving the joystick to the left closes the grapple. Conversely, moving the joystick to the right opens the grapple. Moving the joystick back extends the tip boom cylinder and raises the tip boom. Moving the joystick forward lowers the tip boom. Rotating the joystick counterclockwise causes the grapple to rotate counterclockwise. Rotating the joystick clockwise causes the grapple to rotate clockwise.
Additionally, there are four levers mounted behind the left joystick that control the outriggers. Two of the levers extend and retract the horizontal movement of the two outriggers. The other two levers extend and retract the vertical movement of the outriggers.
I understand that John Deere Company might be using a three-function mechanical joystick for operating the blade of a bulldozer. However, I am not familiar with the details of either the structure or the operation of the joystick.